|[http://www.ncert.nic.in/ncerts/textbook/textbook.htm?jemh1=5-14 NCERT Textbook Class - X - Mathematics - Chapter - 5 - Arithmetic Progressions] | |[http://www.ncert.nic.in/ncerts/textbook/textbook.htm?jemh1=5-14 NCERT Textbook Class - X - Mathematics - Chapter - 5 - Arithmetic Progressions] |